Transverse ultra-thin insulated gate bipolar transistor having high current density

ABSTRACT

A transverse ultra-thin insulated gate bipolar transistor having current density includes: a P substrate, where the P substrate is provided with a buried oxide layer thereon, the buried oxide layer is provided with an N epitaxial layer thereon, the N epitaxial layer is provided with an N well region and P base region therein, the P base region is provided with a first P contact region and an N source region therein, the N well region is provided with an N buffer region therein, the N well region is provided with a field oxide layer thereon, the N buffer region is provided with a P drain region therein, the N epitaxial layer is provided therein with a P base region array including a P annular base region, the P base region array is located between the N well region and the P base region, the P annular base region is provided with a second P contact region and an N annular source region therein, and the second P contact region is located in the N annular source region. The present invention greatly increases current density of a transverse ultra-thin insulated gate bipolar transistor, thus significantly improving the performance of an intelligent power module.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a US National Stage of International Application No. PCT/CN2012/087710, filed 27 Dec. 2012, which claims the benefit of a Chinese Application No. CN20101442085.X, filed 7 Nov. 2012, the entire content of which is fully incorporated by reference herein.

FIELD OF THE INVENTION

The present invention relates to power semiconductor devices, and in particular, to a transverse ultra-thin insulated gate bipolar transistor (IGBT) having current density that is integrated on an ultra-thin process platform.

DESCRIPTION OF RELATED ART

Intelligent power modules in high-voltage power integrated circuits can be applied to various fields, for example, driving and controlling various industrial and civil single-phase and three-phase motors. A power switch element in an intelligent power module is a key part in the entire intelligent power module. As a power switch element, an IGBT not only is characterized by a high working speed, large input impedance, and a simple driving circuit of a MOSFET, but also has an advantage of a large current carrying capacity of a bipolar transistor. Therefore, during recent years, IGBTs are frequently used in power integrated circuits. In IGBTs, the L-IGBT attracts our attention as it is suitable to be integrated in a high-density integrated circuit. A large-capacity current output capability is very important in power devices. However, for an ultra-thin L-IGBT, it is very difficult to improve the current density as a conductivity modulation effect is not obvious enough. How to obtain a large current and a high breakdown voltage at a source end and a drain end of the ultra-thin L-IGBT becomes the key to improve the performance of the entire integrated circuit. Therefore, how the ultra-thin L-IGBT functioning as a power switch element obtains high current density undoubtedly is important content of an intelligent power module circuit and process research.

There are already various current density increasing methods for existing L-IGBTs. In the current density increasing methods, a most effective and prominent one is to increase current density of a thick-film L-IGBT in a dual channel manner, which is mentioned in the U.S. Pat. No. 5,731,603 of Toshiba Corporation. In the structure, a P base region has an N epitaxial layer on both sides. Therefore, after a conducting channel is formed on two sides of an N source region, the N epitaxial layer can provide a current flow path. However, in an ultra-thin-film structure, a P base region easily extends to a buried oxide layer below and thus causes an N epitaxial layer that can provide a current flow path to be pinched off. Therefore, the current density increasing method mentioned in the U.S. Pat. No. 5,731,603 is impracticable in the ultra-thin structure.

SUMMARY OF THE INVENTION Technical Problem

The present invention provides a transverse ultra-thin IGBT having current density. The present invention solves the problem of low current density of an ultra-thin L-IGBT, and increases current density without reducing a breakdown voltage.

Technical Solution

A transverse ultra-thin IGBT having high current density includes: a P substrate, where the P substrate is provided with a buried oxide layer thereon, the buried oxide layer is provided with an N epitaxial layer thereon, the thickness of the N epitaxial layer is 0.1 to 2 μm, the N epitaxial layer is provided with an N well region and a P base region therein, the N well region is provided with an N buffer region therein, the N well region is provided with a field oxide layer thereon, a boundary of the N buffer region abuts against a boundary of the field oxide layer, the N buffer region is provided with a P drain region therein, and the P base region is provided with a first P contact region and an N source region therein, the N epitaxial layer is provided therein with a P base region array including a P annular base region, the P base region array is located between the N well region and the P base region, the P annular base region is provided with a second P contact region and an N annular source region therein, the second P contact region is located in the N annular source region, a first polysilicon gate is disposed on a surface of a boundary region on which the field oxide layer and the N annular source region are adjacent, the first polysilicon gate extends from the boundary of the field oxide layer towards a direction of the N annular source region to a place above the N annular source region, a first gate oxide layer is disposed below an extension region of the first polysilicon gate, a second polysilicon gate is disposed above the N epitaxial layer, a boundary of the second polysilicon gate extends to the place above the N annular source region, another boundary of the second polysilicon gate extends to a place above the N source region, a second gate oxide layer is disposed below the second polysilicon gate, a dielectric isolation oxide layer is disposed on the field oxide layer, the first polysilicon gate, the second polysilicon gate, the P base region, the P annular base region, the first P contact region, the N source region, the second P contact region, the N annular source region, the N buffer region, and the P drain region, an emitter metal wire is connected to the first P contact region, the N source region, the second P contact region, and the N annular source region, a collector metal wire is connected to the P drain region, and a gate metal wire is connected to the first polysilicon gate and the second polysilicon gate.

Advantageous Effect

Compared with the prior art, the present invention has the following advantages:

The transverse ultra-thin IGBT having high current density of the present invention uses a new structure, that is, the N epitaxial layer (3) is provided therein with the P base region array (17) including the P annular base region (6 b), and the P base region array (17) is located between the N well region (4) and the P base region (6 a). Compared with a conventional transverse ultra-thin IGBT (FIG. 3) having only one P base region, the present invention achieves that after a gate voltage increases constantly, a depletion layer first occurs below the gate oxide layers of the P base region (6 a) and the P annular base region (6 b), and after the gate voltage reaches a threshold voltage, an inversion layer occurs below the gate oxide layers of the P base region (6 a) and the P annular base region (6 b), which is equivalent to addition of a conducting channel of a parasitic NMOS transistor in the transverse ultra-thin IGBT, that is, increase of a current of the parasitic NMOS transistor. As shown in FIG. 1, the N epitaxial layer (3) in the x direction and the y direction further can provide a current flow path, and thus the current of the parasitic NMOS transistor can be used as a base region current of a PNP transistor in the transverse ultra-thin IGBT, so that an electro hole collecting capability is added to the first P contact region (7 a) and the second P contact region (7 b) of the P base region (6 a) and the P annular base region (6 b). Finally, current density of the transverse ultra-thin IGBT is improved.

(2) Because the P base region (6 a) and the P base region array (17) including the P annular base region (6 b) cause increase of a quantity of conducting channels, compared with the conventional transverse ultra-thin IGBT having high current density of the present invention has higher current density under the condition of a same withstand voltage, or has a higher withstand voltage under the condition of same current density.

(3) The transverse ultra-thin IGBT having high current density of the present invention is totally based on an existing transverse ultra-thin IGBT manufacturing process, no additional process step is added, and manufacturing is simple.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a transverse ultra-thin IGBT having high current density according to the present invention;

FIG. 2 is a transverse sectional view along I-I′ line in FIG. 1;

FIG. 3 is a transverse sectional view along II-II′ line in FIG. 1;

FIG. 4 is a transverse sectional view of a structure of a conventional transverse ultra-thin IGBT;

FIG. 5 is a diagram of comparison between current density of a transverse ultra-thin IGBT having high current density (proposed structure) according to the present invention and a conventional transverse ultra-thin IGBT (conventional structure);

FIG. 6 is a diagram of comparison between current density after increase of a line quantity of a P base region array including a P annular base region of a transverse ultra-thin IGBT having high current density according to the present invention;

FIG. 7 is a diagram of comparison between current density after change of a spacing between a P base region and a P annular base region of a transverse ultra-thin IGBT having high current density according to the present invention; and

FIG. 8 is a diagram of comparison between current density after change of a spacing between adjacent boundaries of adjacent P annular base regions of a transverse ultra-thin IGBT having high current density according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, FIG. 2, and FIG. 3, a transverse ultra-thin IGBT having high current density includes: a P substrate 1, where the P substrate 1 is provided with a buried oxide layer 2 thereon, the buried oxide layer 2 is provided with an N epitaxial layer 3 thereon, the thickness of the N epitaxial layer 3 is 0.1 to 1.5 μm, the N epitaxial layer 3 is provided with an N well region 4 and a P base region 6 a therein, the N well region 4 is provided with an N buffer region 5 therein, the N well region 4 is provided with a field oxide layer 11 thereon, a boundary of the N buffer region 5 abuts against a boundary of the field oxide layer 11, the N buffer region 5 is provided with a P drain region 9 therein, and the P base region 6 a is provided with a first P contact region 7 a and an N source region 8 a therein, the N epitaxial layer 3 is provided therein with a P base region array 17 including a P annular base region 6 b, the P base region array 17 is located between the N well region 4 and the P base region 6 a, the P annular base region 6 b is provided with a second P contact region 7 b and an N annular source region 8 b therein, the second P contact region 7 b is located in the N annular source region 8 b, a first polysilicon gate 12 a is disposed on a surface of a boundary region on which the field oxide layer 11 and the N annular source region 8 b are adjacent, the first polysilicon gate 12 extends from the boundary of the field oxide layer 11 towards a direction of the N annular source region 8 b to a place above the N annular source region 8 b, a first gate oxide layer 10 a is disposed below an extension region of the first polysilicon gate 12 a, a second polysilicon gate 12 b is disposed above the N epitaxial layer 3, a boundary of the second polysilicon gate 12 b extends to the place above the N annular source region 8 b, another boundary of the second polysilicon gate 12 b extends to a place above the N source region 8 a, a second gate oxide layer 10 b is disposed below the second polysilicon gate 12 b, a dielectric isolation oxide layer 13 is disposed on the field oxide layer 11, the first polysilicon gate 12 a, the second polysilicon gate 12 b, the P base region 6 a, the P annular base region 6 b, the first P contact region 7 a, the N source region 8 a, the second P contact region 7 b, the N annular source region 8 b, the N buffer region 5, and the P drain region 9, an emitter metal wire 14 is connected to the first P contact region 7 a, the N source region 8 a, the second P contact region 7 b, and the N annular source region 8 b, a collector metal wire 15 is connected to the P drain region 9, and a gate metal wire 16 is connected to the first polysilicon gate 12 a and the second polysilicon gate 12 b.

The P base region array 17 may have multiple lines and multiple columns, and may also have multiple lines and a single line. In this embodiment, a P base region array has one column is selected as the P base region array 17 including the P annular base region 6 b, of which a line quantity is not limited, which may be 2, 3, . . . , 10 or more as long as it is ensured that a spacing between adjacent boundaries of P annular base regions is not changed, that is, a path region on which a current can flow is not changed. Current density is little affected by increase of the line quantity of the P base region array 17 including the P annular base region 6 b.

Refer to FIG. 6 for a diagram of comparison between current density after the increase of the line quantity of the P base region array 17 including the P annular base region 6 b.

In this embodiment, the current density may be further improved by using the following technical measures:

(1) A spacing between adjacent boundaries of the P base region (6 a) and the P annular base region (6 b) is 0.5 to 3 μm. If the spacing between the adjacent boundaries of the P base region (6 a) and the P annular base region (6 b) is less than 0.5 μm, a region on which a current can flow is excessively small, the current density can be improved but the effect is not obvious. If the spacing between the adjacent boundaries of the P base region (6 a) and the P annular base region (6 b) is greater than 3 μm, a current flow path is excessively long, and the current density can also be improved but the effect is not obvious. Refer to FIG. 7 for a diagram of comparison between current density after change of the spacing between the adjacent boundaries of the P base region (6 a) and the P annular base region (6 b).

(2) A spacing between adjacent boundaries of adjacent P annular base regions is 1 to 6 μm. If the spacing between the adjacent boundaries of the adjacent P annular base regions is less than 1 μm, a region on which a current can flow is excessively small, the current density can be improved but the effect is not obvious. If the spacing between the adjacent boundaries of the adjacent P annular base regions is greater than 6 μm, and the current density can also be improved but the effect is not obvious. Refer to FIG. 8 for a diagram of comparison between current density after change of the spacing between the adjacent boundaries of the adjacent P annular base regions.

The present invention uses the following method for manufacturing:

1. Select and clean a P silicon substrate, deposit an oxide layer, then perform epitaxy, silicon nitride deposition, photo etching, and ion implantation to phosphorous to generate an N well region, and perform annealing, silicon nitride removal, photo etching, and ion implantation to boron to generate a P base region and a P annular base region.

2. Implant ions to arsenic and phosphorous to generate an N buffer region, perform silicon nitride deposition and photo etching to form an active region, etch silicon nitride, then perform field oxide growth and field implantation, adjust a channel threshold voltage, then perform gate oxide layer growth, deposit and etch polysilicon to form a first polysilicon gate, a second polysilicon gate, and a polysilicon field plate, perform source and drain implantation to form an N source region, an N annular source region, a first P contact region, a second P contact region, and a P drain region, and then deposit a field oxide layer.

3. Etch the field oxide layer to form metal electrode lead-out holes of the N source region, the N annular source region, the first P contact region, the second P contact region, the first polysilicon gate, the second polysilicon gate, and the P drain region, deposit a metal layer, and etch the metal layer to form lead-out electrodes of the N source region, the N annular source region, the first P contact region, and the second P contact region of the transverse ultra-thin IGBT, lead-out electrodes of the first polysilicon gate and the second polysilicon gate, and a lead-out electrode of the P drain region. Finally, perform passivation processing. 

What is claimed is:
 1. A transverse ultra-thin insulated gate bipolar transistor having high current density, comprising: a P substrate (1), wherein the P substrate (1) is provided with a buried oxide layer (2) thereon, the buried oxide layer (2) is provided with an N epitaxial layer (3) thereon, the thickness of the N epitaxial layer (3) is 0.1 to 1.5 μm, the N epitaxial layer (3) is provided with an N well region (4) and a P base region (6 a) therein, the N well region (4) is provided with an N buffer region (5) therein, the N well region (4) is provided with a field oxide layer (11) thereon, a boundary of the N buffer region (5) abuts against a boundary of the field oxide layer (11), the N buffer region (5) is provided with a P drain region (9) therein, and the P base region (6 a) is provided with a first P contact region (7 a) and an N source region (8 a) therein, wherein the N epitaxial layer (3) is provided therein with a P base region array (17) comprising a P annular base region (6 b), the P base region array (17) is located between the N well region (4) and the P base region (6 a), the P annular base region (6 b) is provided with a second P contact region (7 b) and an N annular source region (8 b) therein, the second P contact region (7 b) is located in the N annular source region (8 b), a first polysilicon gate (12 a) is disposed on a surface of a boundary region on which the field oxide layer (11) and the N annular source region (8 b) are adjacent, the first polysilicon gate (12) extends from the boundary of the field oxide layer (11) towards a direction of the N annular source region (8 b) to a place above the N annular source region (8 b), a first gate oxide layer (10 a) is disposed below an extension region of the first polysilicon gate (12 a), a second polysilicon gate (12 b) is disposed above the N epitaxial layer (3), a boundary of the second polysilicon gate (12 b) extends to the place above the N annular source region (8 b), another boundary of the second polysilicon gate (12 b) extends to a place above the N source region (8 a), a second gate oxide layer (10 b) is disposed below the second polysilicon gate (12 b), a dielectric isolation oxide layer (13) is disposed on the field oxide layer (11), the first polysilicon gate (12 a), the second polysilicon gate (12 b), the P base region (6 a), the P annular base region (6 b), the first P contact region (7 a), the N source region (8 a), the second P contact region (7 b), the N annular source region (8 b), the N buffer region (5), and the P drain region (9), an emitter metal wire (14) is connected to the first P contact region (7 a), the N source region (8 a), the second P contact region (7 b), and the N annular source region (8 b), a collector metal wire (15) is connected to the P drain region (9), and a gate metal wire (16) is connected to the first polysilicon gate (12 a) and the second polysilicon gate (12 b).
 2. The transverse ultra-thin insulated gate bipolar transistor having high current density according to claim 1, wherein the P base region array (17) comprising the P annular base region (6 b) is a P base region array having one column.
 3. The transverse ultra-thin insulated gate bipolar transistor having high current density according to claim 1, wherein the P annular base region (6 b) is hexagonal, quadrilateral, or circular.
 4. The transverse ultra-thin insulated gate bipolar transistor having high current density according to claim 1, wherein a spacing between adjacent boundaries of the P base region (6 a) and the P annular base region (6 b) is 0.5 to 3 μm.
 5. The transverse ultra-thin insulated gate bipolar transistor having high current density according to claim 1, wherein a spacing between adjacent boundaries of adjacent P annular base regions (6 b) is 1 to 6 μm.
 6. The transverse ultra-thin insulated gate bipolar transistor having high current density according to claim 2, wherein the P annular base region (6 b) is hexagonal, quadrilateral, or circular. 